1. Field of the Invention
This invention relates to the field of dot matrix print heads.
2. Description of the Prior Art
Printing characters by the dot-matrix method commonly involves the use of a printing head wherein a plurality of printing styli are arranged in a vertical column, and spaced apart a distance equal to the vertical distance between rows of the matrix. It is often the case that the distance between rows is equal to the stylus wire diameter and in such a case, the wires are actually touching. The stylus array is rapidly moved across a printing medium and the styli selectively actuated by electromagnetic means to form groups of dots which convey the form of the desired character. There may be, for example, 7 styli in the vertical column spaced about 0.014 inches apart so as to print characters about 0.100 high. Each character may consist of dots selected from a matrix 7 dots high .times. 7 dots wide.
It is obviously impractical to construct electromagnetic actuating structures small enough to be spaced 0.014 inches apart, so what has evolved in the art is the use of long (typically about 31/2 inches) styli which are gradually curved so that the remote ends are far enough apart to allow them to be driven by reasonably sized actuators. Actuators are distributed in a manner which minimizes the curvature of the styli, typically in a circular pattern, the driven ends of the styli being near the center of the circle.
While practical, there are a number of problems associated with the above described configuration, and some of these problems are exacerbated when the number of styli is increased, as for example, in the case of an array of 14 styli in two columns. Increasing the number of styli to 14 can be advantageous in many instances since substantially higher writing speeds can be achieved with a two column configuration, but the additional curvature of the wire needed and the generally larger units, make the wire driving and guiding a more difficult matter.